1. Field of the Invention
The present invention relates to an inductosyn type absolute value scale and an absolute value calculating method.
2. Description of the Related Art
An inductosyn type scale employed in machine tools and the like includes a rotary type (a rotary scale) and a linear type (a linear scale).
The rotary scale is for detecting a rotation angle, and is configured of: a rotor on a rotating side having a rotor side coil pattern 1 folded in a zigzag manner and formed into an annular shape on the whole as shown in FIG. 27A; and a stator on a fixed side having a stator side coil pattern 2 folded in a zigzag manner and formed into an annular shape on the whole as shown in FIG. 27B. Here, the rotor and the stator are disposed to face each other so that the rotor side coil pattern 1 and the stator side coil pattern 2 can face each other.
In this rotary scale, when an alternating current is supplied to the stator side coil pattern 2, an induced voltage is generated on the rotor side coil pattern 1. As shown in FIG. 28, the induced voltage varies periodically (where a period=one pitch of the rotor side coil pattern 1) with a rotation angle of the rotor (the rotor side coil pattern 1) (i.e. with variation in the degree of electromagnetic coupling corresponding to variation in a positional correlation between the stator side coil pattern 2 and the rotor side coil pattern 1). This induced voltage is transmitted from the rotating side to the fixed side through transformers incorporated respectively in the rotating side and the fixed side. Accordingly, the rotation angle of the rotor (a rotating shaft joined to the rotor in a machine tool or the like) can be detected by use of an amount of variation in this induced voltage.
Although illustration is omitted herein, the linear scale is for detecting an amount of linear displacement, and is configured of: a slider on a sliding side having a slider side coil pattern folded in a zigzag manner and formed into a linear shape on the whole; and a scale on a fixed side having a scale side coil pattern folded in a zigzag manner and formed into a linear shape on the whole. Here, the slider and the scale are disposed to face each other so that the slider side coil pattern and the scale side coil pattern can face each other.
In this linear scale, when an alternating current is supplied to the slider side coil pattern, an induced voltage that varies periodically is generated on the scale side coil pattern. The induced voltage varies periodically (where a period=one pitch of the scale side coil pattern) with an amount of linear displacement of the slider (the slider side coil pattern) (i.e. with variation in the degree of electromagnetic coupling corresponding to variation in a positional correlation between the slider side coil pattern and the scale side coil pattern). Accordingly, it is possible to detect the amount of linear displacement (a linear movement distance) of the slider (such as a linear motion shaft of a machine tool or the like joined to the slider) by use of an amount of variation in this induced voltage.
Moreover, a rotary absolute value scale capable of detecting an absolute value of a rotation angle (an absolute angle) and a linear absolute value scale capable of detecting an absolute value of an amount of linear displacement (an absolute amount of displacement) are also developed today as absolute value scales obtained by applying the inductosyn type rotary scale and the inductosyn type linear scale as described above.
The rotary absolute value scale is configured of: a rotor on a rotating side having two rotor side coil patterns 5 and 6 with different pitches which are folded in a zigzag manner and formed into annular shapes on the whole as shown in FIG. 29A; and a stator on a fixed side having two stator side coil patterns 7 and 8 with different pitches which are folded in a zigzag manner and formed into annular shapes on the whole as shown in FIG. 29B. Here, the rotor and the stator are disposed to face each other so that the rotor side coil patterns 5 and 6 can face the stator side coil patterns 7 and 8, respectively. Moreover, the rotor side coil patterns 5 and 6 are provided with different pitches Pm [degrees] and Ps [degrees] (where Ps<Pm), respectively, and are formed in the same plane. The stator side coil patterns 7 and 8 are also provided with different pitches Pm′ [degrees] and Ps′ [degrees] (where Ps′<Pm′), respectively, corresponding to the pitches Pm and Ps of the rotor side coil patterns 5 and 6, and are formed in the same plane.
The configuration of the stator will now be described more in detail with reference to FIGS. 30A and 30B. As shown in FIGS. 30A and 30B, the stator side coil patterns 7 and 8 are formed on a stator 9 by attaching a copper foil onto a surface of a base member 10 with an insulating member 11 interposed therebetween, and then processing this copper foil by use of lithography or the like to form predetermined coil patterns. Moreover, a wiring groove 14 is formed on the base member 10 so that the stator side coil patterns 7 and 8 are electrically connected to an external wire 15 through an internal wire 13 that is provided in this wiring groove 14. A secondary coil 12 of a transformer 16 is also provided in the wiring groove 14 formed on the base member 10. Although illustration is omitted herein, the rotor has a configuration similar to the stator, and is obtained by forming the rotor side coil patterns 5 and 6 by use of a copper foil attached onto a base member with an insulating member interposed therebetween. Here, an internal wire and a primary coil of the transformer 16 are provided in a wiring groove that is formed on the base member.
In this rotary absolute value scale, when an alternating current is supplied to the stator side coil patterns 7 and 8, induced voltages are generated on the rotor side coil patterns 5 and 6. The induced voltages vary periodically (where a period=each of one pitch Ps and one pitch Pm of the rotor side coil patterns 5 and 6) with rotation angles of the rotor (the rotor side coil patterns 5 and 6). These induced voltages are respectively transmitted from the rotating side to the fixed side through the transformers 16 incorporated in the rotating side and the fixed side. Accordingly, it is possible to detect the absolute angle of the rotor (such as a rotating shaft of a machine tool or the like joined to the rotor) by use of a difference in the detected angle between the amounts of variation in these induced voltages.
The linear absolute value scale is configured of: a slider on a sliding side having two slider side coil patterns 21 and 22 with different pitches which are folded in a zigzag manner and formed into linear shapes on the whole as shown in FIG. 31A; and a scale on a fixed side having two scale side coil patterns 23 and 24 with different pitches which are folded in a zigzag manner and formed into linear shapes on the whole as shown in FIG. 31B. Here, the slider and the scale are disposed to face each other so that the slider side coil patterns 21 and 22 can face the scale side coil patterns 23 and 24, respectively. Moreover, the scale side coil patterns 23 and 24 are provided with different pitches Pm [mm] and Ps [mm] (where Ps<Pm), respectively, and the slider side coil patterns 21 and 22 are also provided with different pitches Pm′ [degrees] and Ps′ [degrees] (where Ps′<Pm′), respectively corresponding to the pitches Pm and Ps of the scale side coil patterns 23 and 24, which are formed in the same plane.
The configuration of the slider will now be described more in detail with reference to FIGS. 32A and 32B. As shown in FIGS. 32A and 32B, the slider side coil patterns 21 and 22 are formed on a slider 25 by attaching a copper foil onto a surface of a base member 26 with an insulating member 27 interposed therebetween and then by processing this copper foil to form predetermined coil patterns by use of lithography or the like. Moreover, a wiring groove 28 is formed on the base member 26 so that the slider side coil patterns 21 and 22 can be electrically connected to an external wire 30 through an internal wire 29 that is provided in this wiring groove 28. Although illustration is omitted herein, the scale is configured as similar to the slider by forming the scale side coil patterns 23 and 24 by use of a copper foil attached onto a base member with an insulating member interposed therebetween. Here, the scale side coil patterns 23 and 24 are electrically connected to an external wire through an internal wire that is provided in a wiring groove formed on the base member.
In this linear absolute value scale, when an alternating current is supplied to the slider side coil patterns 21 and 22, induced voltages are generated on the scale side coil patterns 23 and 24. The induced voltages vary periodically (where a period=each of one pitch Ps and one pitch Pm of the scale side coil patterns 23 and 24) with amounts of linear displacement of the scale (the scale side coil patterns 23 and 24). Accordingly, the absolute amount of displacement of the slider (such as a linear motion shaft of a machine tool or the like joined to the slider) can be detected by use of a difference in the amount of displacement between the amounts of variation in these induced voltages.
<Patent Document 1> Japanese Patent Application Laid-open Publication No. Hei 11-083545
In the case of the conventional rotary absolute value scale described above, the rotor side coil patterns 5 and 6 are formed in the same plane while the stator side coil patterns 7 and 8 are also formed in the same plane. Accordingly, in order to avoid an increase in the size of the entire absolute value scale, it is inevitable to reduce the space occupied by each of the coil patterns 5, 6, 7, and 8 (the lengths in a radial direction of each of the coil patterns 5, 6, 7, and 8). As a consequence, detection accuracy is more likely to be affected by manufacturing variation among the absolute value scales, and thus stable detection accuracy is difficult to obtain.
Similarly, in the case of the conventional linear absolute value scale described above, the slider side coil patterns 21 and 22 are formed in the same plane while the scale side coil patterns 23 and 24 are also formed in the same plane. Accordingly, in order to avoid an increase in the size of the entire absolute value scale, it is inevitable to reduce the space occupied by each of the coil patterns 21, 22, 23, and 24 (the lengths in a width direction of each of the coil patterns 21, 22, 23, and 24). As a consequence, detection accuracy is prone to be affected by manufacturing variation among the absolute value scales, and thus stable detection accuracy is difficult to obtain.
Moreover, there has also been a demand for a calculation method capable of easily and reliably calculating the absolute angle or the absolute amount of displacement with the absolute value scale.